That same Locus Poll also listed the top 15 Fantasy novels from last century.
Again asterisked means I’ve read them, ** that I can’t remember and (*) only the first of the trilogy.
1(*) Tolkien, J. R. R. : The Lord of the Rings (1955)
2* Martin, George R. R. : A Game of Thrones (1996)
3 Tolkien, J. R. R. : The Hobbit (1937)
4* Le Guin, Ursula K. : A Wizard of Earthsea (1968)
5* Zelazny, Roger : Nine Princes in Amber (1970) 971 70
6 Lewis, C. S. : The Lion, the Witch and the Wardrobe (1950)
7* Miéville, China : Perdido Street Station (2000)
8 Rowling, J. K. : Harry Potter and the Philosopher’s Stone (1997)
9* Crowley, John : Little, Big (1981)
10* Adams, Richard : Watership Down (1972)
11 Goldman, William : The Princess Bride (1973)
12* Martin, George R. R. : A Storm of Swords (2000)
13 Beagle, Peter S. : The Last Unicorn (1968)
14** White, T. H. : The Once and Future King (1958)
15 Pratchett, Terry (& Gaiman, Neil) : Good Omens (1990)
I don’t have quite such a high hit rate here – unsurprisingly, as I prefer Science Fiction to Fantasy: but there is of course a lot of crossover between the two and the boundary is blurred. Even so I would have said Perdido Street Station was SF rather than Fantasy.